jwpstayman nailed my first thought exactly. What SC’s are you using? I bought D7.2’s soon after they came out replacing the former D7’s and in my well treated dedicated listening room with all tubed gear they have never sounded bright per se to my ears but yes, speaker cables make a huge difference in my experience. I have Cardas Clear SC’s and Auditorium 23 SC’s and the Auditoriums really tame the highs with the Spendors.
The Spendor haters kind of tick me off until I calm down and remind myself that there is no reason to give two sh*ts what they think.
System synergy is real. It could be your choice of amp, preamp, interconnects, digital rig, or room or all or some in combination.
Auditorium 23’s are amazing speaker cables. They are not easy to come by new at the moment so you may need to source a used pair. The Auditoriums with my Spendor 7.2’s and with my Devore O/93’s (I rotate them every six months for grins) do tone, texture, timbre, and space better than my Cardas. The Cardas excel at dynamic drive, snap, pin-point imaging, and deep bass.
If you check out the gear used by S'Phile reviewers, last time I checked more than half of them had Auditorium 23 SC's in their arsenal. For ~$900 new they are amazing.